fix build version

[metachris]

📝 Summary

make wouldn't set the build version correctly because it was a const instead of var.

---

✅ I have run these commands

• make lint
• make test-race
• go mod tidy

[codecov-commenter]

Codecov Report

Merging #542 (ec6b851) into develop (54eeaa2) will increase coverage by 1.12%.
The diff coverage is 67.22%.

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@@             Coverage Diff             @@
##           develop     #542      +/-   ##
===========================================
+ Coverage    70.24%   71.36%   +1.12%     
===========================================
  Files            6        8       +2     
  Lines          541     1177     +636     
===========================================
+ Hits           380      840     +460     
- Misses         132      301     +169     
- Partials        29       36       +7     

Flag	Coverage Δ
unittests	71.36% <67.22%> (+1.12%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cli/main.go	0.00% <0.00%> (ø)
cli/types.go	0.00% <0.00%> (ø)
server/mock_types.go	100.00% <ø> (ø)
server/types.go	66.15% <66.15%> (ø)
server/service.go	83.08% <82.27%> (+11.07%)	⬆️
server/utils.go	82.58% <85.15%> (+15.01%)	⬆️
server/mock_relay.go	90.30% <95.04%> (+7.44%)	⬆️
server/relay_entry.go	90.00% <100.00%> (+8.75%)	⬆️

... and 1 file with indirect coverage changes